Initial surface roughness of electrochemical plating copper under different conditions

The uniformity and morphology during electrochemical plating of copper film is extremely important in Copper interconnect processing. However, the uniformity and morphology of plated copper film can be strongly influenced by process conditions. It is well known that additives in copper plating bath is believed to be a key to achieve bottom-up filling. For copper plating in the trench and via with smaller size, the initial surface roughness is an important factor that links to the elimination of void in copper film. Initial surface roughness should be reduced in order to prevent impinging caused by surface roughness in small feature. In this paper, we complete a set of experiments to investigate the relationship between surface roughness and additives in copper plating bath. A simple model is developed to explain the relationship between initial roughness and additives, and Chronoamperometry curves derived from electrochemical workstation are measured to confirm the rationality of the simple model.